Assessment of Sport Fish Distribution and Relative Abundance in the LRDR, Alberta, Phase II
Jason Blackburn and Jason Cooper
Fish species distribution and abundance was assessed on 450 km of the Lower Red Deer River (LRDR) using electrofishing. A total of 90 1-km reaches were sampled of a predetermined 95 sample reaches. Species distribution and abundance, and total abundance by section, were determined from capture totals, visual counts, and catchper- unit-effort (CPUE). Goldeye and shorthead redhorse displayed the broadest distributions, as well as the greatest abundance throughout the study area. Sauger was the next most abundant and widely distributed sport fish species, followed by walleye, burbot, mooneye, and northern pike. Sections with the highest total abundance of fish were section 1 near Joffre, downstream of the Highway 11 bridge crossing, and sections 12 to 13 near Buffalo and Bindloss, toward the confluence with the South Saskatchewan River near the Alberta - Saskatchewan border. The total number of fish observed during sampling differed substantially from the total number captured, with 1,116 fish observed compared with only 429 captured. Capture success was low (inefficient) and possibly linked to water turbidity, with reduced success in clear water. Overall sample efficiency was highest via visual counts in clear water, with 58% of all tallied fish made by visual counts in three resampled sections. Comparison of abundance data collected in 2004 with that collected between 1990 - 1991 revealed a statistically significant decline in total relative fish abundance from an average of 25.5 fish/km in 1990 – 1991 to 5.3 fish/km in 2004. In particular, significant decreases in abundance were observed for goldeye, sauger, walleye, white sucker, shorthead redhorse, longnose sucker, and quillback sucker. There was no significant change in relative abundance of burbot, mountain whitefish, northern pike, lake whitefish or lake sturgeon. Declines in abundance were attributed to sampling inefficiency in 2004 and/or the effects of consecutive drought years prior to the assessment. Species composition between assessments was similar; however, species distribution patterns were typically smaller and more fragmented in 2004. Species richness was greater in 2004 than the previous survey and was probably the result of a larger study area and greater sampling effort. In comparison to the assessment in 1990 - 1991, aging structures collected in 2004 indicated slower growth rates in goldeye and mooneye, but faster rates for walleye and sauger. Use of a broader variety of sampling methods is recommended to increase capture success, and an angler creel survey could be used to verify anecdotal reports of increased sauger catches in recent years. A comprehensive habitat assessment of the LRDR should be conducted to assist future conservation measures to ensure sustainability of the fishery. Additional focused sampling of the data deficient species quillback and sauger should be undertaken, encompassing other southern Alberta river systems to ensure sufficient data capture. Long-term monitoring of declining sauger and goldeye populations should also be initiated.